fs/xfs/xfs_behavior.h - maze/linux - Git at Google

 /*
  * Copyright (c) 2000-2003,2005 Silicon Graphics, Inc.
  * All Rights Reserved.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
  * published by the Free Software Foundation.
  *
  * This program is distributed in the hope that it would be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write the Free Software Foundation,
  * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  */
 #ifndef __XFS_BEHAVIOR_H__
 #define __XFS_BEHAVIOR_H__

 /*
  * Header file used to associate behaviors with virtualized objects.
  *
  * A virtualized object is an internal, virtualized representation of
  * OS entities such as persistent files, processes, or sockets.  Examples
  * of virtualized objects include vnodes, vprocs, and vsockets.  Often
  * a virtualized object is referred to simply as an "object."
  *
  * A behavior is essentially an implementation layer associated with
  * an object.  Multiple behaviors for an object are chained together,
  * the order of chaining determining the order of invocation.  Each
  * behavior of a given object implements the same set of interfaces
  * (e.g., the VOP interfaces).
  *
  * Behaviors may be dynamically inserted into an object's behavior chain,
  * such that the addition is transparent to consumers that already have
  * references to the object.  Typically, a given behavior will be inserted
  * at a particular location in the behavior chain.  Insertion of new
  * behaviors is synchronized with operations-in-progress (oip's) so that
  * the oip's always see a consistent view of the chain.
  *
  * The term "interposition" is used to refer to the act of inserting
  * a behavior such that it interposes on (i.e., is inserted in front
  * of) a particular other behavior.  A key example of this is when a
  * system implementing distributed single system image wishes to
  * interpose a distribution layer (providing distributed coherency)
  * in front of an object that is otherwise only accessed locally.
  *
  * Note that the traditional vnode/inode combination is simply a virtualized
  * object that has exactly one associated behavior.
  *
  * Behavior synchronization is logic which is necessary under certain
  * circumstances that there is no conflict between ongoing operations
  * traversing the behavior chain and those dynamically modifying the
  * behavior chain.  Because behavior synchronization adds extra overhead
  * to virtual operation invocation, we want to restrict, as much as
  * we can, the requirement for this extra code, to those situations
  * in which it is truly necessary.
  *
  * Behavior synchronization is needed whenever there's at least one class
  * of object in the system for which:
  * 1) multiple behaviors for a given object are supported,
  * -- AND --
  * 2a) insertion of a new behavior can happen dynamically at any time during
  *     the life of an active object,
  *	-- AND --
  *	3a) insertion of a new behavior needs to synchronize with existing
  *	    ops-in-progress.
  *	-- OR --
  *	3b) multiple different behaviors can be dynamically inserted at
  *	    any time during the life of an active object
  *	-- OR --
  *	3c) removal of a behavior can occur at any time during the life of
  *	    an active object.
  * -- OR --
  * 2b) removal of a behavior can occur at any time during the life of an
  *     active object
  *
  */

 /*
  * Behavior head.  Head of the chain of behaviors.
  * Contained within each virtualized object data structure.
  */
 typedef struct bhv_head {
 	struct bhv_desc *bh_first;	/* first behavior in chain */
 } bhv_head_t;

 /*
  * Behavior descriptor.	 Descriptor associated with each behavior.
  * Contained within the behavior's private data structure.
  */
 typedef struct bhv_desc {
 	void		*bd_pdata;	/* private data for this behavior */
 	void		*bd_vobj;	/* virtual object associated with */
 	void		*bd_ops;	/* ops for this behavior */
 	struct bhv_desc *bd_next;	/* next behavior in chain */
 } bhv_desc_t;

 /*
  * Behavior identity field.  A behavior's identity determines the position
  * where it lives within a behavior chain, and it's always the first field
  * of the behavior's ops vector. The optional id field further identifies the
  * subsystem responsible for the behavior.
  */
 typedef struct bhv_identity {
 	__u16	bi_id;		/* owning subsystem id */
 	__u16	bi_position;	/* position in chain */
 } bhv_identity_t;

 typedef bhv_identity_t bhv_position_t;

 #define BHV_IDENTITY_INIT(id,pos)	{id, pos}
 #define BHV_IDENTITY_INIT_POSITION(pos) BHV_IDENTITY_INIT(0, pos)

 /*
  * Define boundaries of position values.
  */
 #define BHV_POSITION_INVALID	0	/* invalid position number */
 #define BHV_POSITION_BASE	1	/* base (last) implementation layer */
 #define BHV_POSITION_TOP	63	/* top (first) implementation layer */

 /*
  * Plumbing macros.
  */
 #define BHV_HEAD_FIRST(bhp)	(ASSERT((bhp)->bh_first), (bhp)->bh_first)
 #define BHV_NEXT(bdp)		(ASSERT((bdp)->bd_next), (bdp)->bd_next)
 #define BHV_NEXTNULL(bdp)	((bdp)->bd_next)
 #define BHV_VOBJ(bdp)		(ASSERT((bdp)->bd_vobj), (bdp)->bd_vobj)
 #define BHV_VOBJNULL(bdp)	((bdp)->bd_vobj)
 #define BHV_PDATA(bdp)		(bdp)->bd_pdata
 #define BHV_OPS(bdp)		(bdp)->bd_ops
 #define BHV_IDENTITY(bdp)	((bhv_identity_t *)(bdp)->bd_ops)
 #define BHV_POSITION(bdp)	(BHV_IDENTITY(bdp)->bi_position)

 extern void bhv_head_init(bhv_head_t *, char *);
 extern void bhv_head_destroy(bhv_head_t *);
 extern int  bhv_insert(bhv_head_t *, bhv_desc_t *);
 extern void bhv_insert_initial(bhv_head_t *, bhv_desc_t *);

 /*
  * Initialize a new behavior descriptor.
  * Arguments:
  *   bdp - pointer to behavior descriptor
  *   pdata - pointer to behavior's private data
  *   vobj - pointer to associated virtual object
  *   ops - pointer to ops for this behavior
  */
 #define bhv_desc_init(bdp, pdata, vobj, ops)		\
  {							\
 	(bdp)->bd_pdata = pdata;			\
 	(bdp)->bd_vobj = vobj;				\
 	(bdp)->bd_ops = ops;				\
 	(bdp)->bd_next = NULL;				\
  }

 /*
  * Remove a behavior descriptor from a behavior chain.
  */
 #define bhv_remove(bhp, bdp)				\
  {							\
 	if ((bhp)->bh_first == (bdp)) {			\
 		/*					\
 		* Remove from front of chain.		\
 		* Atomic wrt oip's.			\
 		*/					\
 	       (bhp)->bh_first = (bdp)->bd_next;	\
 	} else {					\
 	       /* remove from non-front of chain */	\
 	       bhv_remove_not_first(bhp, bdp);		\
 	}						\
 	(bdp)->bd_vobj = NULL;				\
  }

 /*
  * Behavior module prototypes.
  */
 extern void		bhv_remove_not_first(bhv_head_t *bhp, bhv_desc_t *bdp);
 extern bhv_desc_t *	bhv_lookup(bhv_head_t *bhp, void *ops);
 extern bhv_desc_t *	bhv_lookup_range(bhv_head_t *bhp, int low, int high);
 extern bhv_desc_t *	bhv_base(bhv_head_t *bhp);

 /* No bhv locking on Linux */
 #define bhv_lookup_unlocked	bhv_lookup
 #define bhv_base_unlocked	bhv_base

 #endif /* __XFS_BEHAVIOR_H__ */
	/*
	* Copyright (c) 2000-2003,2005 Silicon Graphics, Inc.
	* All Rights Reserved.
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License as
	* published by the Free Software Foundation.
	*
	* This program is distributed in the hope that it would be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
	*/
	#ifndef __XFS_BEHAVIOR_H__
	#define __XFS_BEHAVIOR_H__

	/*
	* Header file used to associate behaviors with virtualized objects.
	*
	* A virtualized object is an internal, virtualized representation of
	* OS entities such as persistent files, processes, or sockets. Examples
	* of virtualized objects include vnodes, vprocs, and vsockets. Often
	* a virtualized object is referred to simply as an "object."
	*
	* A behavior is essentially an implementation layer associated with
	* an object. Multiple behaviors for an object are chained together,
	* the order of chaining determining the order of invocation. Each
	* behavior of a given object implements the same set of interfaces
	* (e.g., the VOP interfaces).
	*
	* Behaviors may be dynamically inserted into an object's behavior chain,
	* such that the addition is transparent to consumers that already have
	* references to the object. Typically, a given behavior will be inserted
	* at a particular location in the behavior chain. Insertion of new
	* behaviors is synchronized with operations-in-progress (oip's) so that
	* the oip's always see a consistent view of the chain.
	*
	* The term "interposition" is used to refer to the act of inserting
	* a behavior such that it interposes on (i.e., is inserted in front
	* of) a particular other behavior. A key example of this is when a
	* system implementing distributed single system image wishes to
	* interpose a distribution layer (providing distributed coherency)
	* in front of an object that is otherwise only accessed locally.
	*
	* Note that the traditional vnode/inode combination is simply a virtualized
	* object that has exactly one associated behavior.
	*
	* Behavior synchronization is logic which is necessary under certain
	* circumstances that there is no conflict between ongoing operations
	* traversing the behavior chain and those dynamically modifying the
	* behavior chain. Because behavior synchronization adds extra overhead
	* to virtual operation invocation, we want to restrict, as much as
	* we can, the requirement for this extra code, to those situations
	* in which it is truly necessary.
	*
	* Behavior synchronization is needed whenever there's at least one class
	* of object in the system for which:
	* 1) multiple behaviors for a given object are supported,
	* -- AND --
	* 2a) insertion of a new behavior can happen dynamically at any time during
	* the life of an active object,
	* -- AND --
	* 3a) insertion of a new behavior needs to synchronize with existing
	* ops-in-progress.
	* -- OR --
	* 3b) multiple different behaviors can be dynamically inserted at
	* any time during the life of an active object
	* -- OR --
	* 3c) removal of a behavior can occur at any time during the life of
	* an active object.
	* -- OR --
	* 2b) removal of a behavior can occur at any time during the life of an
	* active object
	*
	*/

	/*
	* Behavior head. Head of the chain of behaviors.
	* Contained within each virtualized object data structure.
	*/
	typedef struct bhv_head {
	struct bhv_desc bh_first; / first behavior in chain */
	} bhv_head_t;

	/*
	* Behavior descriptor. Descriptor associated with each behavior.
	* Contained within the behavior's private data structure.
	*/
	typedef struct bhv_desc {
	void bd_pdata; / private data for this behavior */
	void bd_vobj; / virtual object associated with */
	void bd_ops; / ops for this behavior */
	struct bhv_desc bd_next; / next behavior in chain */
	} bhv_desc_t;

	/*
	* Behavior identity field. A behavior's identity determines the position
	* where it lives within a behavior chain, and it's always the first field
	* of the behavior's ops vector. The optional id field further identifies the
	* subsystem responsible for the behavior.
	*/
	typedef struct bhv_identity {
	__u16 bi_id; /* owning subsystem id */
	__u16 bi_position; /* position in chain */
	} bhv_identity_t;

	typedef bhv_identity_t bhv_position_t;

	#define BHV_IDENTITY_INIT(id,pos) {id, pos}
	#define BHV_IDENTITY_INIT_POSITION(pos) BHV_IDENTITY_INIT(0, pos)

	/*
	* Define boundaries of position values.
	*/
	#define BHV_POSITION_INVALID 0 /* invalid position number */
	#define BHV_POSITION_BASE 1 /* base (last) implementation layer */
	#define BHV_POSITION_TOP 63 /* top (first) implementation layer */

	/*
	* Plumbing macros.
	*/
	#define BHV_HEAD_FIRST(bhp) (ASSERT((bhp)->bh_first), (bhp)->bh_first)
	#define BHV_NEXT(bdp) (ASSERT((bdp)->bd_next), (bdp)->bd_next)
	#define BHV_NEXTNULL(bdp) ((bdp)->bd_next)
	#define BHV_VOBJ(bdp) (ASSERT((bdp)->bd_vobj), (bdp)->bd_vobj)
	#define BHV_VOBJNULL(bdp) ((bdp)->bd_vobj)
	#define BHV_PDATA(bdp) (bdp)->bd_pdata
	#define BHV_OPS(bdp) (bdp)->bd_ops
	#define BHV_IDENTITY(bdp) ((bhv_identity_t *)(bdp)->bd_ops)
	#define BHV_POSITION(bdp) (BHV_IDENTITY(bdp)->bi_position)

	extern void bhv_head_init(bhv_head_t , char );
	extern void bhv_head_destroy(bhv_head_t *);
	extern int bhv_insert(bhv_head_t , bhv_desc_t );
	extern void bhv_insert_initial(bhv_head_t , bhv_desc_t );

	/*
	* Initialize a new behavior descriptor.
	* Arguments:
	* bdp - pointer to behavior descriptor
	* pdata - pointer to behavior's private data
	* vobj - pointer to associated virtual object
	* ops - pointer to ops for this behavior
	*/
	#define bhv_desc_init(bdp, pdata, vobj, ops) \
	{ \
	(bdp)->bd_pdata = pdata; \
	(bdp)->bd_vobj = vobj; \
	(bdp)->bd_ops = ops; \
	(bdp)->bd_next = NULL; \
	}

	/*
	* Remove a behavior descriptor from a behavior chain.
	*/
	#define bhv_remove(bhp, bdp) \
	{ \
	if ((bhp)->bh_first == (bdp)) { \
	/* \
	* Remove from front of chain. \
	* Atomic wrt oip's. \
	*/ \
	(bhp)->bh_first = (bdp)->bd_next; \
	} else { \
	/* remove from non-front of chain */ \
	bhv_remove_not_first(bhp, bdp); \
	} \
	(bdp)->bd_vobj = NULL; \
	}

	/*
	* Behavior module prototypes.
	*/
	extern void bhv_remove_not_first(bhv_head_t bhp, bhv_desc_t bdp);
	extern bhv_desc_t * bhv_lookup(bhv_head_t bhp, void ops);
	extern bhv_desc_t * bhv_lookup_range(bhv_head_t *bhp, int low, int high);
	extern bhv_desc_t * bhv_base(bhv_head_t *bhp);

	/* No bhv locking on Linux */
	#define bhv_lookup_unlocked bhv_lookup
	#define bhv_base_unlocked bhv_base

	#endif /* __XFS_BEHAVIOR_H__ */